1. Field of the Invention
The present invention relates to a manual chain block, and more specifically to a manual chain block having a load sheave supported rotatably between a pair of side plates so that the load sheave can be rotated by an actuating operation of an actuating mechanism having a hand wheel to wind up and unwind a load chain looped around the load sheave.
2. Description of Prior Art
In a conventional manual chain block adapted to rotate a load sheave by operating an actuating mechanism having a hand wheel, for example as disclosed in the Japanese Utility Model Publication No. Sho. 40 (1965)--8997, a wheel cover for covering the actuating mechanism is attached to an outerside of a side plate.
As shown in FIG. 15, this wheel cover has introducing openings 103, 104 for a hand chain 102 looped around a hand wheel 101, formed in a lower portion of a cover body 100 on its opposite sides relative to the hand wheel 101 and a lower cover side wall 105 so formed integrally with the cover body 100 between those introducing openings 103, 104 to define lower opening edges of the introducing openings 103, 104 with the cover body 100. The cover body 100 is fixedly secured by a plurality of stay bolts 106 to an actuating mechanism side side plate 107 of two side plates 107, 108 for supporting a load sheave (not illustrated).
Incidentally, in FIG. 15, the symbol 109 designates a gear cover and the symbol 110 , denotes a hand chain guide.
The wheel cover having the above-mentioned constitution is formed from a sheet metal, and the lower cover side wall 105 defining the lower opening edges of the introducing openings 103, 104 is formed integrally with the cover body 100 by a pending process. Because the lower cover side wall 105 is formed of the sheet metal similarly to the cover body 100 and pushed and secured to the side plate 107 by tightening nuts 111 threadably engaged with the stay bolts 106, its strength is insufficient. Therefore, the cover side wall 105 is formed comparatively wide as shown in FIG. 15.
While the opposite side edges of the cover side wall 105 define the introducing openings 103, 104, the cover side wall 105 is formed wide for attaining its sufficient strength. Accordingly, the opposite side edges of the cover side wall 105 come close the introducing passages of the hand chain 102 passing through the introducing openings 103, 104. When the hand chain 102 is operated abruptly and violently to jump up or when a large load is imposed to the hand chain 102 to incline the whole of the chain block, the hand chain 102 is brought into contact with the edges of the cover side wall 105. The resulting rubbing causes unpleasant noises to be generated and the cover side wall 105 is deformed by repetition of the contact for a long term use. There is also a problem in that the cover side wall 105 is deformed and damaged by an impact imposed from outside thereto so that the hand chain 102 is hindered from passing during a normal usage.